Atomization is the mechanical subdivision of liquid into drops. Although the terminology is not standard, drops can be broken into several size categories. Spraying creates coarse drops in the range of 100-1,000 microns in diameter. A mist is typically considered to be fine drops in the 10-100 micron range while nebulizing creates very fine drops under 10 microns in diameter. Nebulized liquids are generally preferred in inhalation aerosol therapy.
To produce the very fine drops desired for inhalation therapy, prior art inhalers generally use a gas propellant. Although these gas-powered inhalers work well, they result in the release of the propellants into the atmosphere. Some of these propellants may be chlorinated fluorocarbons which are known to be quite damaging to the ozone layer. Hydrocarbons are also used, but are also not beneficial to the atmosphere. In addition, some hydrocarbons may react adversely with some medications.